Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Century Aluminum Co. (NASDAQ:CENX) jumped 10% after being upgraded by an analyst.

So what: JPMorgan Chase analyst Michael Gambardella increased both Century Aluminum and the better-known Alcoa to "overweight" because he thinks higher aluminum prices will help earnings. The company won't report earnings until at least mid-February, and Alcoa missed expectations for the fourth quarter, so the improvement Gambardella is expecting may not hit until later this year.

Now what: Stocks will often rise or fall short-term after an analyst rating change, but the truth is that Wall Street gets its calls wrong more often than not. Use this as a data point in your analysis but not the only reason to either buy or sell the stock. Long-term, it's earnings growth that will drive Century Aluminum, and we'll find out more about where earnings are headed sometime next month.